Common Name: Texas Walnut

General Information

Juglans microcarpa is a deciduous shrub or a tree that can grow from 6 - 15 metres tall. Trees are often multi-trunked or even shrubby[, ].
The plant is harvested from the wild for local use as a food and source of materials. Its wood is of good quality but the plant is not common enough to be commercially exploited[]
Juglans microcarpa has a wide native range, far exceeding the boundaries for a threatened category. In this range, the species occurs in narrow habitats where it is common. No major threats to the species are reported and it is rarely used for timber. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2018)[].

Known Hazards

None known

Botanical References

, ,

Range

South-western N. America - Kansas, Oklahoma, New Mexico, Texas to northeast Mexico.

Habitat

Moister areas in sub-arid climates, growing in riparian woodland communities in stream bottoms, canyons, river beds and the edges and arroyos of the Chihuahuan desert[]. Limestone banks of streams[, ].

Properties

Conservation Status	Least Concern
Edibility Rating
Other Uses Rating
Habit	Deciduous Tree
Height	10.00 m
Pollinators	Wind
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

Requires a deep well-drained loam and a sunny position sheltered from strong winds[, ]. Prefers a slightly alkaline soil[]. This species often experiences drought in its native range[].
There is potential for the species to be planted and used in the face of climate change as it is tolerant of dry conditions[].
Plants produce a deep taproot and they are intolerant of root disturbance[, ]. Seedlings should be planted out into their permanent positions as soon as possible and given some protection for their first winter or two since they are somewhat tender when young[, ].
Flower initiation depends upon suitable conditions in the previous summer[]. The flowers and young growths can be destroyed by even short periods down to -2°c, but fortunately plants are usually late coming into leaf[].
Any pruning should only be carried out in late summer to early autumn or when the plant is fully dormant otherwise wounds will bleed profusely and this will severely weaken the tree[].
Trees have a dense canopy which tends to reduce plant growth below them. We have no specific information for this species, but the roots of several members of this genus produce substances that are toxic to many plant species, especially apples (Malus species), members of the Ericaceae, Potentilla spp and the white pines (certain Pinus spp.)[]. The leaves of many species also secrete substances that have an inhibitory affect on plants growing underneath them. All in all this is not a very good companion plant[].
Closely related to J. major, and hybridizes with that species where their ranges overlap[].

Edible Uses

Seed - raw. The seed is sweet and oily but it is rather small and has a thick shell[, , , , ]. The seed is the smallest of this genus[]. The globose fruits are 14 - 23mm in diameter, containing a nut 11 - 17mm in diameter[].

An edible oil is obtained from the seed, it tends to go rancid quickly.

Medicinal

None known

Agroforestry Uses:

The plant's ability to tolerate drought has led to it being grown in mixed shelterbelts in the southwestern USA[].
Plants produce chemicals which can inhibit the growth of other plants. These chemicals are dissolved out of the leaves when it rains and are washed down to the ground below, reducing the growth of plants under the tree[, , ]. The roots of many members of this genus produce substances that are toxic to many plant species, especially apples (Malus species), members of the Ericaceae, Potentilla spp and the white pines (certain Pinus spp.)[].

Other Uses

Sometimes used as a rootstock[].

The wood is heavy, hard, not strong. It makes a beautiful veneer and has been very over-exploited in the wild for this purpose[]. It is also used in cabinet making, furniture, panelling etc[, , ]. A good quality wood, though its commercial use is rare as the tree is not common[].

Propagation

The seed is best sown as soon as it is ripe in individual deep pots in a cold frame[]. You need to protect it from mice, birds, squirrels etc. The seed usually germinates in late winter or the spring. Plant out the seedlings into their permanent positions in early summer and give some protection from the cold for their first winter or two.
The seed can also be stored in cool moist conditions (such s the salad compartment of a fridge) over the winter and sown in early spring but it may then require a period of cold stratification before it will germinate[, , ].